The generally accepted time and temperature conditions which define when a food product is fully cooked is an internal temperature of the food product of at least 160 degrees Fahrenheit. Upon reaching this internal temperature, it has been determined that virtually all bacterial pathogens in the food product are rendered non-pathogenic. Because meat and poultry food products are predominantly water, if internal temperatures of food product of at least 160 degrees Fahrenheit are achieved rapidly, such as through frying, broiling or grilling, moisture is driven from the food product. As a result, the food product is rendered dry, tasteless and generally unappealing. While raising the temperature of the food product slowly results in the lowest dissipation of moisture, such extended cooking is not possible in many restaurants, particularly fast food restaurants. Hence, processors of meat and poultry products, such as de-boned chicken or ground beef meat patties, deliver such products to restaurants in frozen, but precooked, states. That is, the internal temperature of the product was raised to at least 160 degrees Fahrenheit at the food processing facility. Cooking time at a restaurant is therefore reduced as the frozen food product need only be thawed and warmed to a palatable temperature.
To effect gradual cooking of the food product to minimize water loss, food processors have utilized horizontally oriented linear cookers or vertically oriented spiral steam cookers. Spiral steam cookers are often preferred due to lesser floor space requirements. Because of their configuration, spiral steam cookers provide extended exposure of the food product to boiling water temperatures in order to gradually elevate internal temperatures of the food product. Examples of spiral steam cookers are seen in U.S. Pat. Nos. 4,363,263; 4,582,047 and 4,737,373. The steam temperature and, thus, the cooking chamber in such prior art spiral steam cookers is maintained at a constant, typically from at least 160 to about 212 degrees Fahrenheit.
A problem with these and other prior art spiral steam cookers and related cooking methods is the inability to reach a uniform internal product temperature and the extended time required for raising the internal temperature of the food product to the required temperature of at least 160 degrees Fahrenheit. Such extended cooking times prevents high rates of production of cooked food product. Some of these problems may be linked to these steam cookers not quickly and evenly breaking down the thermal barriers of the food products to be cooked.
In addition, where steam temperatures in prior art cookers are elevated, they are often too high to optimize the desirable moisture content of the food product and are not uniform throughout the cavity of the cooker. However, a reduction in steam temperature to maximize moisture content would further prolong cooking times.
Hence, prior to the present invention, a need existed for a spiral spray cooker which results in higher rates of heat transfer production of cooked food product, which provided a more even distribution of the heat transfer throughout the product, while utilizing reduced vapor temperatures to preserve the maximum moisture content of the food product by precise internal, equilibration temperature in the center of the product.
U.S. Pat. No. 5,189,948, to Lieberman, (the "'948 patent") discloses one attempt to solve some of these problems. Specifically, the '948 patent uses a lower temperature water vapor spiral cooker with a downwardly flowing source of water underneath the food product to cook the food product. The water underneath the food product is allowed to drip down onto food product beneath it. Art exterior hot water spray is also used to decrease loss of moisture and to help thermalize the food product on the conveyor belt. However, the hot water spray in the '948 patent is only directed inward toward a U-shaped channel that encompasses the food product on both sides of the food product, thereby preventing more direct contact of the water with the food product. In addition, since the water spray only comes from the exterior of the spiral belt, the portion of the food product nearest to the exterior of the spiral belt will have a tendency to cook more quickly than the portion nearest the interior of the spiral belt. Thus, the U-shaped channel and the water spray only being on the exterior of the spiral belt create several problems. In addition, the inlet and outlet of the cooking chamber are not sealed, thereby preventing an optimal cooking atmosphere near and around the inlet and outlet, and thereby allowing for a chimney-like effect to take place. Further, there is significant heat and moisture loss through the inlet and outlet of the cooking apparatus disclosed in the '948 patent. Moreover, the water sprayed from the hot water spray is not recycled back to the sprayers, thereby preventing the flavor-enhancing juices from the food product, which end up in the reservoir, from being re-sprayed onto the food product.
The present invention is directed to solving these and other problems.